drc (version 1.2-0)

W1.2: The two-parameter Weibull functions

Description

'W1.2' is the two-parameter Weibull function where the lower limit is fixed at 0 and the upper limit is fixed at 1, mostly suitable for binomial/quantal responses.

Usage

W1.2(fixed = c(NA, NA), names = c("b", "e"))
  
  W2.2(fixed = c(NA, NA), names = c("b", "e"))

Arguments

fixed

numeric vector. Specifies which parameters are fixed and at what value they are fixed. NAs for parameter that are not fixed.

names

a vector of character strings giving the names of the parameters. The default is reasonable.

Value

• See weibull1.

Details

The two-parameter Weibull model is given by the expression $$f(x) = \exp(-\exp(b(\log(x)-e))).$$ The function is asymmetric about the inflection point, that is the parameter $\exp(e)$.

See Also

Related functions are W1.3, W1.4, weibull1 and weibull2.

Examples

## Fitting a two-parameter Weibull model
model1 <- multdrc(number/total~dose, weights=total,
data=earthworms, fct = W1.2(), type = "binomial")
summary(model1)

rm(model1)